title: Regulation of neuronal connexin-36 channels by pH.
abstract: Neurotransmission through electrical synapses plays an important role in the spike synchrony among neurons and oscillation of neuronal networks. Indeed, electrical transmission has been implicated in the hypersynchronous electrical activity of epilepsy. We have investigated the influence of intracellular pH on the strength of electrical coupling mediated by connexin36 (Cx36), the principal gap junction protein in the electrical synapses of vertebrates. In striking contrast to other connexin isoforms, the activity of Cx36 channels decreases following alkalosis rather than acidosis when it is expressed in Xenopus oocytes and N2A cells. This uncoupling of Cx36 channels upon alkalinization occurred in the vertebrate orthologues analyzed (human, mouse, chicken, perch, and skate). While intracellular acidification caused a mild or moderate increase in the junctional conductance of virtually all these channels, the coupling of the skate Cx35 channel was partially blocked by acidosis. The mutational analysis suggests that the Cx36 channels may contain two gating mechanisms operating with opposing sensitivity to pH. One gate, the dominant mechanism, closes for alkalosis and it probably involves an interaction between the C- and N-terminal domains, while a secondary acid sensing gate only causes minor, albeit saturating, changes in coupling following acidosis and alkalosis. Thus, we conclude that neuronal Cx36 channels undergo unique regulation by pH(i) since their activity is inhibited by alkalosis rather than acidosis. These data provide a novel basis to define the relevance and consequences of the pH-dependent modulation of Cx36 synapses under physiological and pathological conditions.
authors.affiliation: Unit of Experimental Neurology, Department of Research, "Ramón y Cajal" Hospital, Carretera de Colmenar Viejo km 9, 28034-Madrid, Spain.
authors.forename: Daniel
authors.initials: D
authors.lastname: González-Nieto
authors.forename: Juan M
authors.initials: JM
authors.lastname: Gómez-Hernández
authors.forename: Belén
authors.initials: B
authors.lastname: Larrosa
authors.forename: Cristina
authors.initials: C
authors.lastname: Gutiérrez
authors.forename: María D
authors.initials: MD
authors.lastname: Muñoz
authors.forename: Ilaria
authors.initials: I
authors.lastname: Fasciani
authors.forename: John
authors.initials: J
authors.lastname: O'Brien
authors.forename: Agata
authors.initials: A
authors.lastname: Zappalà
authors.forename: Federico
authors.initials: F
authors.lastname: Cicirata
authors.forename: Luis C
authors.initials: LC
authors.lastname: Barrio
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D002642:Chick Embryo; D017630:Connexins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D054351:Electrical Synapses / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D015640:Ion Channel Gating / Q000502:physiology; D051379:Mice; D009474:Neurons / Q000378:metabolism*; D009865:Oocytes / Q000378:metabolism; D014982:Xenopus laevis; D000097004:Gap Junction delta-2 Protein
chemical_list: D017630:Connexins; D000097004:Gap Junction delta-2 Protein